The invention generally relates to operator control of autonomous heavy machinery and specifically to methods for human operators to use autonomous vehicles in agriculture, construction, and open-pit mining.
A significant amount of work has been done to improve the efficiency of heavy machinery in areas such as agriculture, construction, and open-pit mining. In particular, some efforts strive to improve effectiveness of the equipment by providing very accurate position information to the driver or even automatically steering the vehicle.
For processes that require an implement attached to the vehicle, the accuracy of the combined vehicle-implement pair may be insufficient for the overall process, even though the accuracy of the automatically controlled (or sensor-assisted) vehicle would otherwise be adequate. Prior art does not go beyond control of the vehicle to address discrepancies between the accuracy of the vehicle alone versus the accuracy of the vehicle-implement pair.
When the goal of the overall system is to accurately control the path of the implement (rather than the vehicle), there are at least two approaches that can be taken: non-co-located sensing and control, on the one hand, and co-located sensing and control, on the other.
Regarding non-co-located sensing and control, the sensor is not located on the body to be controlled. In such a system, the sensor is on the vehicle, but the object to be controlled is the implementxe2x80x94typically at its point of contact with the ground. The system has a very accurate model of the implement and how it is connected to the vehicle. The position of the implement is inferred from the precisely measured position of the vehicle by a transformation matrix and, possibly, a dynamic model and additional intermediary sensors at the hitch.
The advantages of this method include avoiding the additional costly sensors on the implement and avoiding the relative complexity of vehicle control in the co-located method below. A disadvantage is that this technique may not provide sufficient accuracy at the point of interest due to magnification of sensor error by inaccuracies in the model.
In a co-located sensing and control system, the sensor is located on the body to be controlled. In this case, the sensor could be a position sensor located on the implement. An advantage of this method is that the error signal used in closed-loop feedback control is directly measured at the point of interest and can be more accurate than non-co-located control. Disadvantages are that it requires additional sensors on the implement, a more elaborate controller on the vehicle, and possibly a different controller for each type of implement.
The following patents address aspects such as GPS position sensing for machine control and path planning, but do not discuss control of implements nor ways to calibrate the implement:
Parkinson et al., U.S. Pat. No. 6,052,647, xe2x80x9cMethod and System for Automatic Control of Vehicles Based on Carrier Phase Differential GPS,xe2x80x9d describes an auto control system for a land vehicle based on carrier phase differential GPS for position and heading sensing.
Gudat et al., U.S. Pat. No. 5,646,843, xe2x80x9cApparatus and Method for Surface Based Vehicle Control System,xe2x80x9d and Gudat et al., U.S. Pat. No. 5,615,116, xe2x80x9cApparatus and Method for Autonomous Vehicle Navigation Using Path Data,xe2x80x9d discuss auto control of a land vehicle with distinct operating modes and path following. Simple methods for switching between autonomous and manual modes are described.
Brandt et al., U.S. Pat. No. 6,085,130, xe2x80x9cMethod and Apparatus for Selecting a Transition Scheme for Use in Transitioning a Mobile Machine from a First Path to a Second Pathxe2x80x9d relates to the transition from one path to another path, presumably under complete autonomy.
Zimmerman et al., U.S. Pat. No. 6,041,870, xe2x80x9cMethod and Apparatus for Steering a Dozing Machine,xe2x80x9d describes actuation of a dozer blade to laterally adjust the centerline of the vehicle.
Keller et al., U.S. Pat. No. 5,987,383, xe2x80x9cForm Line Following Guidance System,xe2x80x9d covers a method for automatically generating paths.
Rao, U.S. Pat. No. 5,684,696, xe2x80x9cSystem and Method for Enabling an Autonomous Vehicle to Track a Desired Path,xe2x80x9d describes generation of a desired trajectory based on current location and desired trajectory.
Sarangapani et al., U.S. Pat. No. 6,064,926, xe2x80x9cMethod and Apparatus for Determining an Alternate Path in Response to Detection of an Obstacle,xe2x80x9d Sarangapani, U.S. Pat. No. 6,173,215, xe2x80x9cMethod for Determining a Desired Response to Detection of an Obstacle,xe2x80x9d and Sarangapani, U.S. Pat. No. 5,752,207, xe2x80x9cMethod and Apparatus for Determining a Path for a Machine between a Predetermined Route and a Final Position,xe2x80x9d all describe automatic path planning and obstacle avoidance.
Motz et al., U.S. Pat. No. 6,236,924, xe2x80x9cSystem and Method for Planning the Operations of an Agricultural Machine in a Field,xe2x80x9d describes a path planning method.
The following patents pertain to vehicle control:
Motz et al., U.S. Pat. No. 6,205,381, xe2x80x9cSystem and Method for Planning the Operations of an Agricultural Machine in a Field,xe2x80x9d relates to coordination of multiple vehicles under automatic control.
Staub et al., U.S. Pat. No. 6,236,916, xe2x80x9cAutoguidance System and Method for an Agricultural Machine,xe2x80x9d relates to general auto control of farm tractors.
Gharsalli et al., U.S. Pat. No. 6,062,317, xe2x80x9cMethod and Apparatus for Controlling the Direction of Travel of an Earthworking Machine,xe2x80x9d relates to control systems for construction scraper.
Sin et al., U.S. Pat. No. 5,657,226, xe2x80x9cSystem and Method for Causing an Autonomous Vehicle to Track a Path,xe2x80x9d relates to general auto control of farm tractor.
The following patents address aspects of implement control, but do not discuss ways to adjust the implement based on observed performance. These patents also deal with actuated implements only:
Gharsalli et al., U.S. Pat. No. 6,062,317, xe2x80x9cMethod and Apparatus for Controlling the Direction of Travel of an Earthworking Machine,xe2x80x9d discusses use of the implement to affect the steering on an earth-grader type of vehicle.
Gharsalli et al., U.S. Pat. No. 6,062,317, xe2x80x9cMethod and Apparatus for Controlling the Direction of Travel of an Earthworking Machine,xe2x80x9d discusses methods for planning operations of an agricultural machine in a field. Information about a work implement (a model) is provided to the system, but no provision to calibrate based on performance is discussed.
Lombardi, U.S. Pat. No. 6,129,155, xe2x80x9cMethod and Apparatus for Controlling a Work Implement Having Multiple Degrees of Freedom,xe2x80x9d Bailey et al., U.S. Pat. No. 5,987,371, xe2x80x9cApparatus and Method for Determining the Position of a Point on a Work Implement Attached to and Movable Relative to a Mobile Machine,xe2x80x9d Skinner et al., U.S. Pat. No. 6,185,493, xe2x80x9cMethod and Apparatus for Controlling an Implement of a Work Machine,xe2x80x9d and Wiechman, U.S. Pat. No. 6,099,236, xe2x80x9cApparatus for Controlling Movement of an Implement Relative to a Frame of a Work Machine,xe2x80x9d all discuss control of implements using hydraulic actuators and linear and rotary sensors to infer position. No provision to calibrate implement based on performance is discussed.
Krieg et al., U.S. Pat. No. 6,286,606, xe2x80x9cMethod and Apparatus for Controlling a Work Implement,xe2x80x9d and Meduna, et al., U.S. Pat. No. 6,295,746, xe2x80x9cMethod and Apparatus for Controlling Movement of a Work Implement,xe2x80x9d discuss changing control modes on a grader-type implement. No provision is made to calibrate the implement based on observed performance.
Herein is taught a system including a mobile vehicle, an implement, a position sensor, a controller, a user interface (a touch-screen monitor, video monitor or keypad, as examples), a software program to compute a calibration trajectory, and a steering system for steering the vehicle to the desired or adjusted trajectory based on the error between the vehicle""s desired and actual positions.
In one embodiment, non-co-located sensing and control combine with a calibration procedure to help eliminate model error. Another embodiment uses co-located sensing (but not control) to calibrate the model.